NEW ORLEANS (AP) _ Any parent knows that children in day care often bring home flu and runny noses. Now, scientists have found that youngsters sometimes expose their families to more serious infections, such as meningitis.

Several reports presented at a meeting on infectious diseases Tuesday described cases in which outbreaks that spread through day care centers also made parents sick - in some cases, more seriously than the children.

Researchers say one clear messages for parents emerges from their investigations of these episodes: Wash your hands after handling your children.

''It works,'' said Dr. Janet Mohle-Boetani of the Santa Clara County Health Department in California.

At the conference, sponsored by the American Society for Microbiology, health experts described outbreaks in which germs that cause severe diarrhea and meningitis spread from day care centers to the youngsters' homes.

Dr. Cynthia Whitman of the U.S. Centers for Disease Control and Prevention outlined an episode at a Las Vegas day care center last year in which 51 children and six staff members got sick from a particularly nasty form of E. coli.

Ordinarily, E. coli is a harmless resident of people's digestive tracts. But one variety, known in medical shorthand as O157:H7, can make people very sick and even kill. This strain is often passed through undercooked hamburger and unpasteurized milk, but also spreads from person to person.

In the Las Vegas outbreak, 39 percent of the sick children took the infection home to their families. And when this occurred, 19 percent of family members caught the bug.

Those who got sick often had severe, prolonged and bloody diarrhea. One child was so sick that doctors at first thought his bowel had been injured.

In two other cases, both in California, outbreaks of echovirus spread through day care centers and then to the youngsters' families. Typically, these children were only mildly ill, suffering cold symptoms or nausea.

However, their parents sometimes got much sicker, with severe headaches and other symptoms of meningitis.

In an outbreak documented by Mohle-Boetani in Santa Clara County, 18 parents got meningitis, and five of them were hospitalized. Although none of the cases was life-threatening, some of the parents were very ill.

When they conducted tests, they found that 85 percent of the day care children and 60 percent of their parents had been infected with the echovirus.

During the other outbreak last year in Newport Beach, 13 parents were diagnosed with meningitis.

Both E. coli and echovirus are transmitted by contact with contaminated stool. Typically people fail to wash after using the toilet, then pass on the microbes when someone else touches their hands.

The researchers said their investigations show that regular hand washing can break the cycle.

They recommended that parents wash their hands after picking up their youngsters at day care centers, after changing diapers and before eating.

''Day care centers may want to target hand-washing efforts toward the youngest children, who are not toilet trained,'' Whitman said.